JPH0893528A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an air-fuel ratio control device for an internal combustion engine, which calculates an intake pipe wall surface adhering amount in consideration of EGR and has good drivability. In an air-fuel ratio control device for an internal combustion engine, which is equipped with an EGR and which corrects a fuel injection amount according to a wall adhesion amount of an intake pipe to control an air-fuel ratio to be constant, a wall surface according to a return amount of exhaust gas by EGR Wall adhesion correction amount FMW that calculates the adhesion amount QMW and corrects the fuel injection amount based on the wall adhesion amount
And a fuel injection time calculation means for calculating a fuel injection time TAU for correcting the fuel injection amount based on the wall surface adhesion correction amount FMW calculated by the wall surface adhesion correction amount calculation means. Be prepared and configured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine, and more particularly to a vehicle equipped with EGR.
The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine, which corrects the fuel injection amount based on the amount of fuel adhering to the wall surface of the intake pipe in accordance with the amount of exhaust gas returned to the air-fuel ratio.

[0002]

2. Description of the Related Art Generally, fuel injected from a fuel injection valve adheres to a wall surface of an intake pipe to generate fuel which is not sucked into a cylinder of an engine. This fuel is called wall-adhered fuel,
The amount of this fuel is called the amount of adhering to the wall surface. This fuel eventually evaporates and is sent to the combustion chamber of the engine. In the air-fuel ratio control device for an internal combustion engine of the prior art, if the engine is in a steady state, the amount of fuel adhering to the wall surface is constant at the amount determined by the map between the engine speed and the intake pipe negative pressure, and there is no problem. However, it becomes a problem when it is excessive. For example, even if the fuel injection amount is increased during acceleration, the amount of adhering walls increases, so a sufficient amount of fuel is not sent to the combustion chamber. Negative pressure in the tube evaporates and is sent to the combustion chamber, so an excessive amount of fuel is sent. Therefore, in the device disclosed in Japanese Patent Laid-Open No. 63-2154848, the wall adhesion correction that corrects the fuel injection amount by the wall adhesion amount of the intake pipe is performed immediately when the wall adhesion amount changes immediately. Although it was corrected, the fuel injection time TAU may change significantly at the time of sudden acceleration or sudden deceleration, which may cause deterioration of drivability. Therefore, the air-fuel ratio control device for an internal combustion engine disclosed in Japanese Patent Laid-Open No. 5-18289 calculates the fuel injection time TAU at every predetermined cycle depending on whether the wall surface adhesion correction amount FMW exceeds a predetermined guard value. However, the change in TAU was reduced to control the air-fuel ratio, improving drivability.

[0003]

However, in recent years, pollution control vehicles, especially those with a large displacement and high output engine, recirculate a part of the exhaust gas of the engine to the intake side and mix it into the intake mixture. By lowering the maximum temperature during combustion,
EGR (Exhaust Gas Recirculation Device) to reduce NOx production
Equipped. For vehicles equipped with EGR, the temperature of the gas in the intake pipe near the fuel injection valve becomes high when using EGR.
There is a phenomenon that the temperature of the wall surface of the intake pipe rises and the amount of adhesion on the wall surface decreases. However, the air-fuel ratio control devices for internal combustion engines described above and in the related art are not suitable for the EG of vehicles equipped with EGR.
Since the same wall adhesion correction as when not using EGR is performed without considering the point that the wall adhesion correction amount FMW when R is used is reduced, the air-fuel ratio becomes overrich, drivability deteriorates, and emissions are reduced. There is a problem that occurs.

Further, in a vehicle equipped with an EGR equipped with a multi-cylinder engine, the gas temperature in the intake pipe in the vicinity of each cylinder of the multi-cylinder engine depends on the position of a part of the exhaust gas inlet which is returned to the intake side by the EGR. A difference occurs in the wall temperature of the intake pipe. However, since the air-fuel ratio control devices for the internal combustion engine of the above-mentioned and the related art perform the same wall surface adhesion correction for each cylinder, the fuel injection amount sucked into each cylinder when using EGR is close to the introduction port. As the gas temperature in the intake pipe and the wall temperature of the intake pipe become higher, the fuel adhering to the wall surface of the intake pipe evaporates and increases, so that the fuel fed into the combustion chamber becomes excessive. That is, variations occur in the amount of adhesion on the wall surface of each cylinder, the fuel fed into the combustion chamber is not constant in each cylinder, the combustion state of the engine becomes unstable, and the torque generated by the engine fluctuates, as described above. As a result, drivability deteriorates, and there is a problem that emission is generated.

From the above, according to the present invention, in a vehicle equipped with EGR, when the EGR is used, the wall adhering correction is performed in consideration of the adhering amount of the intake pipe wall surface of the fuel, and the air-fuel ratio is controlled to be constant to improve the drivability. The main object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that keeps and does not generate emissions.

Further, according to the present invention, in a multi-cylinder engine equipped with EGR, wall adhering correction is performed in consideration of the position of the inlet of the exhaust gas returned to the intake side by EGR, and the mixture is drawn into each cylinder of the engine. It is possible to provide an air-fuel ratio control device for an internal combustion engine that makes the air uniform, suppresses torque fluctuations between cylinders of the engine, maintains a constant air-fuel ratio to maintain good drivability, and does not generate emissions. To aim.

[0007]

An air-fuel ratio control system for an internal combustion engine according to the present invention, which achieves the above-mentioned main object, comprises an EGR, and corrects the fuel injection amount according to the wall adhering amount of the intake pipe to adjust the air-fuel ratio. In an air-fuel ratio control device for an internal combustion engine, which is controlled to be constant, a wall surface adhesion amount is calculated according to the amount of exhaust gas returned by EGR, and a wall surface adhesion correction amount is calculated to correct the fuel injection amount based on the wall surface adhesion amount. An adhesion correction amount calculation means and a fuel injection time calculation means for calculating a fuel injection time for correcting the fuel injection amount based on the wall surface adhesion correction amount calculated by the wall surface adhesion correction amount calculation means. To do.

In addition to the first embodiment, the air-fuel ratio control apparatus for an internal combustion engine according to the present invention that achieves the above-mentioned other object has a multi-cylinder internal combustion engine, and the wall adhesion correction amount calculation means is provided for each cylinder. It is a means for individually calculating the wall surface adhesion correction amount, and the fuel injection time calculating means is a means for individually calculating the fuel injection time of each cylinder.

[0009]

The air-fuel ratio control system for an internal combustion engine according to the present invention is based on EGR.
In a vehicle equipped with, the wall surface adhesion correction amount calculation means calculates the wall surface adhesion amount QMW according to the amount of exhaust gas returned by the EGR for each predetermined crank angle cycle, and calculates the wall surface adhesion amount QMW _i for the current crank angle cycle. Wall adhesion correction amount FM from the difference from the previous wall surface adhesion amount QMW _{i-1 in} the crank angle cycle
W is calculated, and the fuel injection time TAU is calculated based on the wall surface adhesion correction amount FMW calculated by the fuel injection amount correction means to correct the fuel injection amount and control the air-fuel ratio. Is kept constant.

Further, another air-fuel ratio control system for an internal combustion engine of the present invention is, in a vehicle equipped with an EGR equipped with a multi-cylinder engine, based on the position of the exhaust gas introduction port, the gas temperature in the intake pipe near each cylinder and the intake pipe. The wall surface attachment correction amount FMW of each cylinder is calculated by the wall surface attachment correction amount calculation means in consideration of the wall surface temperature of the cylinder.
Is calculated individually, and the fuel injection amount correction means individually calculates the fuel injection time TAU of each cylinder to correct the fuel injection amount and send it to each cylinder, so that the pressure due to combustion in each cylinder is made uniform, The torque generated in each cylinder of the engine is made uniform to suppress the amount of torque fluctuation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
In the figure, reference numeral 1 is an engine body, 2 is an intake passage, 3 is an air flow meter, 4 is a distributor, 5 is a crank angle reference sensor, 6 is a crank angle sensor, 7 is a fuel injection valve, 8 is a water jacket, and 9 is Water temperature sensor, 10 control circuit, 11 exhaust manifold, 12 catalytic converter, 13 O ₂ sensor, 14 EGR valve, 15 TVV (Thermal Vaccum Valve), 16 valve opening sensor, 17 fuel tank Shown respectively. As shown, an air flow meter 3 is provided in the intake passage 2 of the engine body 1 to directly measure the intake air amount. The air flow meter 3 has a built-in potentiometer, for example, and generates an electric signal of an analog voltage proportional to the intake air amount Q to generate an analog signal A / D converter 101 of the control circuit 10.
Output to. The distributor 4 includes a crank angle reference sensor 5 and a crank angle reference sensor 5 that generate a pulse signal serving as a reference of the crank angle every 720 ° (1 rotation of the cam shaft and 2 rotations of the crank shaft) when the crank shaft is converted into the crank angle. A crank angle sensor 6 is provided which generates a pulse signal for detecting the engine rotation in detail every 30 °. The pulse signals of the crank angle reference sensor 5 and the crank angle sensor 6 are supplied to the input / output interface 102 of the control circuit 10, and the output of the crank angle sensor 6 is supplied to the interrupt terminal of the CPU 103 via the I / O interface 102. To be done.

Further, in the intake passage 2, a fuel injection valve 7 for supplying the pressurized fuel from the fuel tank 17 to the intake port is individually provided for each cylinder. In addition, the engine body 1
The water jacket 8 of the cylinder block is provided with a water temperature sensor 9 for detecting the temperature of the cooling water. The water temperature sensor 9 generates an electric signal of analog voltage according to the temperature THW of the cooling water. This output is also supplied to the A / D converter 101.

In the exhaust system downstream of the intake manifold 11, a catalytic converter 12 containing a three-way catalyst for simultaneously purifying three toxic components HC, CO and NOx in the exhaust gas.
Is provided. An O ₂ sensor 13 is provided on the exhaust manifold 11, that is, on the upstream side of the catalytic converter 12. The O ₂ sensor 13 generates an electric signal according to the oxygen component concentration in the exhaust gas. That is, the O ₂ sensor 13 generates an electric signal of a different analog voltage according to whether the air-fuel ratio is leaner or richer than the stoichiometric air-fuel ratio and outputs it to the A / D converter 101 of the control circuit 10.

Further, the configuration shown in this figure is such that exhaust gas is converted into EGR.
A negative pressure control system EGR that lowers the maximum temperature at the time of combustion and reduces the production of NOx by recirculating to the intake side through the valve 14 and mixing with the intake air-fuel mixture is provided. As shown in the figure, the TVV 15 is provided in the negative pressure passage,
The TVV 15 acts to close the EGR valve 14 when the engine body 1 is cold or at low speed, and when the engine body 1 goes from medium speed to high speed, the negative pressure in the intake pipe increases and the EGR valve 14 opens properly. Act on. EGR
The valve 14 is provided with a valve opening sensor 16 that outputs an analog voltage corresponding to the opening amount of the EGR valve 14. The output of the valve opening sensor 16 is input to the A / D converter 101 and converted into digital by the A / D converter 101.

The control circuit 10 is configured as, for example, a microcomputer, and has a ROM in addition to the A / D converter 101, the input / output interface 102, and the CPU 103.
104, RAM 105, backup RAM 106, clock generator 107, etc. are provided. Further, in the control circuit 10, the down counter 108, the flip-flop 109, and the drive circuit 110 are for controlling the fuel injection valve 7. That is, when the fuel injection time TAU, which is the valve opening time of the fuel injection valve 7 that adjusts the fuel injection amount, is calculated in the routine described later, T
The value of AU is set in the down counter 108 and the flip-flop 109 is also set. As a result, the drive circuit 110 opens the fuel injection valve 7 and sends fuel from the fuel tank 17 to the combustion chamber of the engine body 1. On the other hand, when the down counter 108 down counts the clock signal (not shown) output from the clock generator 107 to the set number, the flip-flop 109 is reset, and the drive circuit 110 closes the fuel injection valve 7 and the fuel tank 17 The fuel supply from the engine to the combustion chamber of the engine body 1 is stopped.

The CPU 103 interrupts the A / D
The error occurs when the input / output interface 102 receives the pulse signal of the crank angle sensor 6 after the A / D conversion of the converter 101 is completed. The intake air amount data Q and the cooling water temperature data THW of the air flow meter 3 are fetched by an A / D conversion routine executed at a predetermined time or at a predetermined crank angle and stored in a predetermined area of the RAM 105. That is, the intake air amount data Q and the cooling water temperature data THW in the RAM 105 are updated every predetermined time. Further, the rotation speed data Ne is calculated by interruption of the crank angle sensor 6 for each 30 ° of the crank angle,
It is stored in a predetermined area of the RAM 105. Next, the calculation processing of the wall surface adhesion correction amount FMW (wall surface adhesion correction amount calculation means) and the calculation processing of the injected fuel time TAU (fuel injection time correction means) according to the present invention will be described, but before that, EGR
The relationship between the amount and the amount of adhesion on the wall is described.

FIG. 2 is a diagram showing the relationship between the load (intake pipe pressure) and the amount of adhered wall surface in the EGR on / off system.
The horizontal axis PM shows the intake pipe pressure, and the vertical axis QMW shows the wall surface adhesion amount. This wall surface adhesion amount QMW is an operating condition parameter, for example, the intake air amount Q / N per one rotation (intake pipe pressure P
Equivalent to M, N indicates engine speed) and rotation speed N
e is determined by using a two-dimensional map of the amount of adhered wall surface stored in advance in the ROM 104. When EGR is off and EGR
Intake pipe pressure P when the rotation speed Ne is constant at the time of ON
The saturated wall surface adhesion amount QMW after complete warming with respect to M is shown. It is shown that when the EGR is on, the gas temperature in the intake pipe and the intake pipe wall surface temperature are higher than when the EGR is off, so that the fuel adhering to the wall surface decreases and the wall surface adhesion amount QMW decreases.

FIG. 3 is a diagram showing a relationship between the EGR amount and the wall surface attachment amount in the EGR amount variable system. Here, the EGR amount means the amount of returning the exhaust gas to the intake side by EGR. Even when the intake pipe pressure PM and the rotation speed Ne are constant, if the EGR amount is adjusted by changing the opening of the EGR valve, the intake pipe gas temperature and the intake pipe wall surface temperature increase as the EGR amount increases, and fuel atomization occurs. Therefore, it is shown that the wall surface adhesion amount QMW decreases as This figure shows the amount of adhered wall surface Q in a saturated state after the EGR amount has been changed and after complete warming up.
It shows MW.

FIG. 4 shows the EGR amount and the wall surface adhesion correction coefficient KFE.
It is a figure which shows the relationship with GR. As shown in FIG.
Since the wall surface adhesion amount QMW decreases as the EGR amount increases, the wall surface adhesion correction coefficient KEFGR for determining the decreased wall surface adhesion amount QMW is shown. The wall adhesion correction coefficient KFEGR is 1 when the EGR amount is 0, and the EGR
It shows that it approaches 0 as the amount increases. This figure also shows the wall surface adhesion amount QMW in the saturated state after the EGR amount is changed and after the complete warming. The calculation processing of the wall surface adhesion correction amount FMW and the calculation processing of the injected fuel time TAU according to the present invention will be described below.

FIG. 5 is a flowchart of a wall surface adhesion correction calculation routine in consideration of EGR according to the first embodiment of the present invention. This drawing shows an embodiment of a variable EGR amount system. Hereinafter, description will be given while alternately referring to FIG. In the figures after this figure, the number following S indicates a step number. The control circuit 10 receives the pulse signal of the crank angle sensor 6 at the interrupt terminal of the CPU 103 via the input / output interface 102, and stores the above-mentioned wall surface adhesion correction coefficient KFEGR in the ROM 104 for each 90 ° crank angle, for example, as shown in FIG. The map is obtained from the map corresponding to the EGR amount and stored in the RAM 105 (step S1). This E
The GR amount is obtained from the valve opening sensor 16 provided in the EGR valve 14 as described above. Next, the basic wall surface adhesion amount qmw _i that does not take EGR into account is obtained from the map when EGR is off described in FIG. 2, and the obtained qmw _i is multiplied by the wall surface adhesion correction coefficient KFEGR obtained in step S1 and The multiplication result is QMW _i . This QMW _i is stored in the RAM 105 as a wall surface adhesion amount in consideration of EGR (step S2). Obtained new wall adhesion QM
Subtract the previously obtained wall adhesion amount QMW _i-1 from W _i ,
The subtraction result is used as the wall surface adhesion correction amount FMW in the RAM 10
5 (step S3). The obtained wall adhesion correction amount FMW is added to the basic fuel injection time TAUP described in FIG. 6 to calculate the fuel injection time TAU (step S).
4).

FIG. 6 is a flow chart of an injection amount calculation routine for calculating the injection fuel time TAU. The process shown in this figure is executed every predetermined crank angle, for example, every 360 °. In step S1, the intake air amount data Q and the rotation speed data Ne are read from the RAM 105 shown in FIG. 1 to calculate the basic fuel injection time TAUP. For example TAU
It is calculated from P ← α · Q / Ne (α is a constant). Step S
In step 2, the final fuel injection time TAU is calculated from the following equation: TAU ← (TAUP + FMW) β + γ (β and γ are correction amounts determined by other operating state parameters). Next, in step S3, the final fuel injection time TAU is set in the down counter 108 shown in FIG.
The flip-flop 109 shown in is set to start fuel injection.

Another embodiment of the present invention which is applied to a multi-cylinder engine equipped with EGR when the EGR rate of each cylinder varies depending on the position of the inlet for returning the exhaust gas due to EGR to the intake side explain. EG of each cylinder
If there is a difference in the R ratio, there is a difference in the gas temperature in the intake pipe and the wall surface temperature around each cylinder, and there is a phenomenon in which the wall surface adhesion amount of each cylinder differs. Here, the EGR rate means the percentage expressed by the following equation. EGR rate = [exhaust gas recirculation flow rate / (intake air amount + exhaust gas recirculation flow rate)] × 100

FIG. 7 shows E for each cylinder of a 4-cylinder engine.
It is a figure which shows the specific example of a GR distribution rate. This EGR distribution ratio is obtained from experimental data, and according to this figure, an example is shown in which the position of the inlet for returning the exhaust gas is provided near cylinder # 3. According to this figure, when the EGR distribution ratio of # 1 is 1.0, # 2 is 0.7, # 3 is 1.2, and # 4.
Is found to be 0.9.

FIG. 8 is a diagram showing a concrete example of the correction coefficient KEGR of the wall surface adhesion amount based on the EGR distribution ratio shown in FIG. From the EGR distribution rate shown in FIG. 7, according to this figure, the correction coefficient KEGR of the wall surface adhesion amount is 1.0 for # 1, 1.2 for # 2, 0.7 for # 3, and 1 for # 4. It turns out that it is 1.

FIG. 9 is a flow chart of a wall surface adhesion correction calculation routine for each cylinder in consideration of EGR according to the second embodiment of the present invention. This drawing shows an embodiment of a variable EGR amount system. Hereinafter, description will be given while alternately referring to FIG. The control circuit 10 outputs the pulse signal of the crank angle sensor 6 to the above-described wall surface adhesion correction coefficient K for each 90 ° crank angle, for example.
The correction coefficient KEGR of the wall surface adhesion amount corresponding to each cylinder described in FIG. Is read and stored in the RAM 105 (step S1). This EGR amount is also obtained from the valve opening sensor 16 provided in the EGR valve 14 as described above. Next, the basic wall surface adhesion amount qmw _i that does not consider EGR is obtained from the map when EGR is off described in FIG. 2, and the obtained qmw _i is the wall surface adhesion correction coefficient KFEGR and the correction coefficient KEGR obtained in step S1. And the multiplication result is QMW _i . This QMW _i is stored in the RAM 105 as a wall surface adhesion amount in consideration of EGR (step S2). The previously obtained wall surface attachment amount QMW _i-1 is subtracted from the obtained new wall surface attachment amount QMW _i , and the subtraction result is the wall surface attachment correction amount F.
It is stored in the RAM 105 as the MW (step S3).
The obtained wall adhesion correction amount FMW is added to the basic fuel injection time TAUP described in FIG. 6 to calculate the fuel injection time TAU (step S4).

FIG. 10 shows the EGR valve opening and the wall surface adhesion amount Q.
It is a time chart explaining the time change of MW,
(A) EGR valve opening, (B) EGR amount, (C)
Is the temperature of the gas in the intake pipe, (D) is the wall temperature of the intake pipe, (E)
Is a time chart showing the change over time of the wall adhesion amount QMW. In (A) to (E) of FIG. 10, the horizontal axis indicates time t. At time t1, the EGR valve opens 60%,
After a lapse of a predetermined time, the EGR amount starts to increase at time t2 and becomes constant after a predetermined time, and the gas temperature in the intake pipe also starts to increase and becomes constant after a predetermined time. At time t3, the intake pipe wall surface temperature starts to increase and becomes constant after a predetermined time. , Wall surface adhesion amount QMW is time t
2 starts to decrease due to the influence of the gas temperature in the intake pipe and becomes constant after a predetermined time, and further starts to decrease at the time t3 due to the influence of the intake pipe wall surface temperature and becomes constant after a predetermined time, and the opening degree of the EGR valve at the time t4. It changes from 60% to 80%, the EGR amount further increases at time t5 after a predetermined time delay and becomes constant after a predetermined time, and the same applies to time t6, t7, t8, t.
9 has elapsed, and the EGR valve is closed from 100% to 0% at time t11, the EG is delayed at time t12 by a predetermined time.
The R amount starts to decrease and becomes constant after a predetermined time, and the gas temperature in the intake pipe also starts to decrease and becomes constant after a predetermined time at time t1.
At 3, the intake pipe wall surface temperature starts decreasing and becomes constant after a predetermined time, and the wall surface adhesion amount QMW starts to increase at time t12 due to the influence of the gas temperature in the intake pipe and becomes constant after a predetermined time at time t12.
13 further increases due to the influence of the intake pipe wall surface temperature, and becomes constant after a predetermined time.

For the sake of convenience of explanation, the wall surface adhesion amount QMW _i obtained in consideration of the EGR amount described with reference to FIGS. 5 and 9 is the EGR amount after the change of the EGR valve opening and the cylinder interior gas temperature. Although the explanation has been made by omitting the transient time when the intake pipe wall surface temperature changes, in reality, as shown in the time chart of FIG. 10, the EGR valve opening degree and the wall surface adhesion amount QM
Since the relationship with W has a time delay, the actual calculation is EG
The EGR amount corresponding to the change in the opening of the R valve is interpolated and obtained momentarily, and the resulting EGR amount is corrected to the wall adhesion correction coefficient KFE in step S1 of FIGS. 5 and 9.
GR is determined and calculation is performed.

Regarding the wall surface adhesion correction in consideration of EGR,
So far, the embodiment of the variable EGR amount system has been described with reference to FIGS. 5 and 9. Next, in the embodiment of the EGR on / off method, a brief description will be given of how to perform the wall surface adhesion correction. The CPU 103 (see FIG. 1) is, for example, 55K
It is controlled so that EGR is turned off at a vehicle speed of less than m / h, and EGR is turned on at a vehicle speed of 55 km / h or more.
When the CPU 103 turns off EGR, E shown in FIG.
ROM of the data map of wall adhesion QMW when GR is off
104 (see FIG. 1) is read, and the CPU 103 uses the EG
When R is turned on, similarly, a data map of the wall surface adhesion amount QMW at the time of EGR shown in FIG. 2 is read from the ROM 104, and thereafter, steps S3 and S4 of FIG. Are steps S3 and S in FIG.
Execute 4.

[0029]

As described above, according to the air-fuel ratio control system for an internal combustion engine of the present invention, in a vehicle equipped with EGR, the gas temperature in the intake pipe is changed according to the amount of exhaust gas returned by EGR when EGR is used. And the wall temperature of the intake pipe are taken into consideration, the wall adhesion correction amount FMW is calculated, and the fuel injection time TAU is calculated.
Is calculated to correct the fuel injection amount and control the air-fuel ratio constant, so that the air-fuel ratio does not become overrich especially during acceleration / deceleration, drivability is improved, and emissions do not occur.

According to another air-fuel ratio control system for an internal combustion engine of the present invention, in a multi-cylinder engine equipped with EGR,
Based on the position of the exhaust gas introduction port in the intake pipe, the wall surface adhesion correction amount FMW of each cylinder is individually calculated in consideration of the gas temperature in the intake pipe near each cylinder and the wall surface temperature of the intake pipe, and Since the fuel injection time TAU is individually calculated and the fuel injection amount is corrected and sent to each cylinder, the pressure due to combustion in each cylinder is made uniform, the torque generated in each cylinder of the engine is made uniform, and the torque fluctuation amount is It is suppressed and the drivability is improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a load and a wall surface adhesion amount in the EGR on / off method.

FIG. 3 is a diagram showing a relationship between an EGR amount and a wall surface adhesion amount in the EGR amount variable system.

FIG. 4 is a diagram showing a relationship between an EGR amount and a wall surface adhesion correction coefficient KFEGR.

FIG. 5 is a flowchart of a wall surface adhesion correction calculation routine in consideration of EGR according to the first embodiment of the present invention.

FIG. 6 is a flowchart of an injection amount calculation routine for calculating an injection fuel time TAU.

FIG. 7 is a diagram showing a specific example of an EGR distribution ratio for each cylinder of a 4-cylinder engine.

8 is a diagram showing a specific example of a correction coefficient KEGR of the amount of adhered wall surface based on the EGR distribution ratio shown in FIG.

FIG. 9 is a flowchart of a wall surface adhesion correction calculation routine of each cylinder in consideration of EGR according to the second embodiment of the present invention.

FIG. 10 is a time chart for explaining changes over time in EGR valve opening and wall surface adhesion amount QMW, where (A) is EGR.
Valve opening, (B) EGR amount, (C) intake pipe gas temperature, (D) intake pipe wall temperature, (E) wall adhesion amount Q
It is a time chart which shows each time change of MW.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine main body 3 ... Air flow meter 4 ... Distributor 5 ... Crank angle reference sensor 6 ... Crank angle sensor 7 ... Fuel injection valve 9 ... Water temperature sensor 10 ... Control circuit 11 ... Exhaust manifold 12 ... Catalytic converter 13 ... O ₂ sensor 14 ... EGR valve 15 ... TVV 16 ... Valve opening sensor 17 ... Fuel tank

Claims (2)

[Claims] 1. An air-fuel ratio control device for an internal combustion engine, comprising an EGR, which corrects a fuel injection amount in accordance with a wall surface adhesion amount of an intake pipe to control an air-fuel ratio constant. The wall surface adhesion correction amount calculation means for calculating the wall surface adhesion amount in accordance with the calculated wall surface adhesion amount and the wall surface adhesion correction amount for correcting the fuel injection amount based on the wall surface adhesion amount, and the wall surface calculated by the wall surface adhesion correction amount calculation means. An air-fuel ratio control device for an internal combustion engine, comprising: a fuel injection time calculating means for calculating a fuel injection time for correcting the fuel injection amount based on an adhesion correction amount. 2. The internal combustion engine is multi-cylinder, the wall surface adhesion correction amount calculation means is a means for individually calculating the wall surface adhesion correction amount for each cylinder, and the fuel injection time calculation means is The air-fuel ratio control device for an internal combustion engine according to claim 1, which is a unit that individually calculates the fuel injection time of each cylinder.